import com.fasterxml.jackson.databind.ObjectMapper;
import com.mysql.jdbc.jdbc2.optional.MysqlDataSource;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.sql.DataSource;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

class Message{
    public String from;
    public String to;
    public String message;

    @Override
    public String toString() {
        return "Message{" +
                "from='" + from + '\'' +
                ", to='" + to + '\'' +
                ", message='" + message + '\'' +
                '}';
    }
}
@WebServlet("/message")
public class MessageServlet extends HttpServlet {
    ObjectMapper objectMapper = new ObjectMapper();
    //private List<Message> messageList = new ArrayList<>();
    private DataSource dataSourse = new MysqlDataSource();

    @Override
    public void init() throws ServletException {
        ((MysqlDataSource) dataSourse).setUrl("jdbc:mysql://127.0.0.1:3306/message_wall?characterEncoding=utf8&useSSL=false");
        ((MysqlDataSource) dataSourse).setUser("root");
        ((MysqlDataSource) dataSourse).setPassword("200456zjr");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Message message = objectMapper.readValue(req.getInputStream(),Message.class);
        System.out.println(message);
        //messageList.add(message);//存到内存中
        try {
            save(message);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
        resp.setStatus(200);
        resp.getWriter().write("OK");
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setStatus(200);
        resp.setContentType("application/json; charset=utf8");
        List<Message> messageList = null;
        try {
            messageList = load();
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
        String respJson = objectMapper.writeValueAsString(messageList);
        resp.getWriter().write(respJson);
    }

    private void save(Message message) throws SQLException {
        //建立连接
        Connection connection = dataSourse.getConnection();
        //构造sql
        String sql = "insert into message values(?,?,?)";
        PreparedStatement statement = connection.prepareStatement(sql);
        statement.setString(1,message.from);
        statement.setString(2,message.to);
        statement.setString(3,message.message);
        //执行
        statement.executeUpdate();
        //关闭
        statement.close();
        connection.close();
    }
    private List<Message> load() throws SQLException {
        Connection connection = dataSourse.getConnection();

        String sql = "select * from message";
        PreparedStatement statement = connection.prepareStatement(sql);

        ResultSet set = statement.executeQuery();

        List<Message> ans = new ArrayList<>();
        while(set.next()){
            Message message = new Message();
            message.from = set.getString("from");
            message.to = set.getString("to");
            message.message = set.getString("message");
            ans.add(message);
        }

        set.close();
        statement.close();
        connection.close();

        return ans;
    }
}
